Philip Alcabes discusses myths of health, disease and risk.

Nuclear Energy and Risk

Elizabeth Kolbert is a fine science writer.  Her explanations of the complicated mechanisms — geothermal, marine chemical, atmospheric, and so forth — underlying climate change are clear and compelling.

But I confess I’m no fan of her work.  Kolbert’s sky-is-falling! rhetoric is a little too florid, and her criticism of people who don’t act environmentally a little too pointed.

Yet, her short piece in this week’s New Yorker, “The Nuclear Risk,” is terrific.  It’s worth reading.   She gets at a central lesson of the radioactivity crisis that followed on the earthquake + tsunami disaster:  you can only plan for the disasters you’re able to conceive of.  The Japanese catastrophe, she writes

illustrates, so starkly and so tragically, [that] people have a hard time planning for events that they don’t want to imagine happening. But these are precisely the events that must be taken into account in a realistic assessment of risk. We’ve more or less pretended that our nuclear plants are safe, and so far we have got away with it. The Japanese have not.

That the nuclear crisis is supposedly under control now, or might be under control if some new problems are dealt with, doesn’t change the planning problem (and have a look at this blog post by Evan Osnos for a worrying take on what happens to people who are facing such a triplex disaster scenario).

Kolbert relates the problem of nuclear planning in the U.S. to corporate interference with regulatory agencies, quoting the Government Accountability Office’s finding that the Nuclear Regulatory Commission has based its policies

on what the industry considered reasonable and feasible to defend against rather than on an assessment of the terrorist threat itself.

It’s disturbing that industry and regulators are on intimate terms, but it isn’t exactly news — not in regard to energy policy, nor health policy (for example, consider the CDC’s Advisory Committee on Immunization Practices, which I wrote about a year ago).   The comfortable collusion between corporations and government agencies is an issue — but it’s not the most troubling lesson of the Japanese crisis.

Rather, the main event is the inevitability of unforeseen and unforeseeable disasters.  And the simple impossibility of making plans to avoid what can’t be imagined.

Which is where I part company with Kolbert.   Would better planning (or stricter regulation of industry) have avoided the near-catastrophic radioactive release at Daichii?  Yes, perhaps.  But nobody could have foreseen an earthquake of this magnitude, or infrastructure so destabilized by a tsunami as fast-moving and destructive as this one, or the double-punch effect occurring where it did and how it did.  There’s only so much you can plan because there’s only so much you can envisage.

And that’s the problem with the idea of planning to reduce risk.  You plan for what you know. Maybe you plan for something a little worse than what you’ve seen before — but even that is basically what you know, with a little juicing to make it livelier.   Even the pure-fantasy regulatory agency — the one with firewall immunity from influence by industry, perfectly competent engineering of its plans, and state-of-the-art technology — can’t foresee every eventuality.  Therefore, even the best planning won’t eliminate risk.

In the end, the question isn’t just how to keep the energy industry away from the regulators.   It’s how to live in a universe that isn’t completely predictable, no matter how good you think your “science” is.   And is ruled by random, implacable, and sometimes highly destructive nature.

Plague Did Not Begin in China. And Why Should Anyone Think It Did?

Nicholas Wade, the NY Times‘s science writer, jumps the gun with a story today asserting that plague began in China.  Maybe it’s understandable:  you don’t often get a front-page story if you’re a science reporter, so once in a while you take some shaky science and turn it into an international incident.

But to understand why the story is wrong means recognizing a weakness of science as it’s often practiced today.

Wade’s claim is based on two papers published this month.  A relatively well done study by Haensch et al. in PLoS Pathogens earlier in October tested human remains from well-identified plague pits — burial sites for medieval plague victims — in different parts of Europe.  Researchers amplified DNA sequences of the plague bacterium, Yersinia pestis, at specific genetic loci, and tested to see whether the DNA matched known sequences of contemporary Y. pestis genes.

The findings published in PLoS suggest that the Black Death and perhaps subsequent waves of plague in Europe were indeed caused by Y. pestis — which would tend to debunk the theory proposed by some British researchers that the Black Death was some kind of viral hemorrhagic fever outbreak.  And they suggest that there were at least two widely different Y. pestis strains involved in different parts of Europe.  Here’s a bit of the abstract:

[O]n the basis of 17 single nucleotide polymorphisms plus the absence of a deletion in glpD gene, our aDNA results identified two previously unknown but related clades of Y. pestis associated with distinct medieval mass graves. These findings suggest that plague was imported to Europe on two or more occasions, each following a distinct route.

The main weakness here is that DNA could not be amplified from all of the plague pits the researchers studied, but after using alternative means to test the DNA debris against contemporary gene sequences the investigators concluded that the absence of genetic material reminiscent of one strain of Y. pestis was evidence that that strain was not in play in that part of Europe at the time.  Probably right, but stretching the available evidence.

It’s a common mistake, alas.  To paraphrase Karl Popper:  just because you see DNA from white swans and don’t see any DNA from black swans, doesn’t mean that black swans don’t exist.

Still, the PLoS paper is persuasive that more than one strain of the plague bacterium was circulating, and probably causing deaths, in the plague period in Europe.  Of course, it says nothing about China.

So where does the NYT reporter get his headline-grabbing story?  A paper to be published in Nature Genetics online (still embargoed at the time I’m writing, but a summary appears here) states that the sequences of plague DNA amplified from plague pit remains, as well as contemporary isolates, can be placed on a molecular clock because of the occurrence of unique mutations.  Winding the clock backward, the researchers conclude that the Ur plague organism, ancestor of all Y. pestis, came from the far east.

The molecular biology may be unimpeachable, but the inferences about history aren’t supportable by molecular evidence.  That might explain why they’re almost certainly wrong.

The problem (scientists, I hope you’re listening!) is that you may know very well what you know, but you can never know what you haven’t seen.  The hereditary tree has its roots in China.  Here is one proposed by some of the same authors in a 2004 PNAS paper:

In this set-up, isolates of Y. pestis from China seem closest to the primordial strains.

But of course, the molecular clock doesn’t take account of strains that are no longer extant.  And ones that haven’t been unearthed.  The contemporary researchers don’t see them (or don’t know how to look), so they don’t exist.

It’s a bad mistake, inferentially.  And historically.  It’s where the NYT writer goes wrong.  Almost certainly, plague did not begin in China.  It began as an enzootic infection of small mammals in the uplands of central Asia.  This is the story convincingly relayed by William H. McNeill in Plagues and Peoples a generation ago, and none of the many accounts I’ve read since then has debunked it.

Plague would have had to begin in an ecosystem in which it could circulate at moderate transmission rates with little pathogenicity among small mammals (the natural host of the bacterium).  Exactly where it started remains open to question, but it was probably in the area that is now Turkestan/Uzbekistan.  With the development of trade between that region and China, intermixing of local (central-Asian) animals with caravan-accompanying rats would have allowed Y. pestis to adapt to the latter.

Quite possibly China was the source of the first human outbreaks of plague — because the river valleys of China were settled and agricultural (therefore offering feeding opportunities for rats as well as multiple opportunities for rat-human interaction) long before Europe was.  That fact probably accounts for the biologists’ (mistaken) belief that their early samples show that Y. pestis started out in China.

But plague began as — and remains — a disease of animals.  To acknowledge that human outbreaks in China preceded the human outbreaks in Europe (the Justinian plague that began in the mid-sixth century, the Black Death that began in the 1340s, and subsequent visitations) is not the same as saying that plague originated in China.

Which it didn’t.  Plague is an animal disease from Central Asia.  Plague’s long history is the usual one:  ecosystem change, trade, animal-human interactions, alterations in climate and economic conditions, and occasional opportunities for mass human illness.   (One world, one health.)

Above all, remember that science is only capable of drawing conclusions about what scientists can observe.  Don’t be taken in by hair-raising stories.  Even in the NY Times.

Bed Bug Worry, Mosquito Mayhem

You hear a lot about bed bugs these days, here in New York City.   The bed bug infestation has become part of New York angst, the newest of our plagues.  The NY Times had its top infectious disease writer cover the recent CDC-EPA joint statement on bed bug control.  There’s even an iPhone app with GPS-enabled bed bug maps of New York and other big cities.

Early this month, a couple of friends, thinking they might splurge on a downtown hotel to celebrate their tenth wedding anniversary, were soliciting bed bug reports before choosing where to stay.  And at a family gathering last week, one young man — recently graduated from an elite college, an intellectual usually given to ironic mockery of the nuttier trends evident in the generation that still uses e-mail — told me that while he’s afraid of bees and doesn’t like mosquitoes, bed bugs really terrify him.

Bed bugs are unpleasant.  Their bites can itch.  Their feces and molted shells can set off asthma attacks or other allergies.  It’s sensible to avoid them, and get rid of them if they’re in your home.  I wrote a few months ago that it makes perfect sense that health authorities do something to limit bed bug woes.

But if you ask me what insects worry me most as a public health professional, I certainly wouldn’t say “bed bugs.”  Ticks, especially as Lyme disease spreads geographically.  Phlebotomine (sand) flies, as leishmaniasis becomes a more serious problem.  Mosquitoes, always.   Bed bugs are far from the top of my list.

The Aedes mosquitoes that carry yellow fever, dengue, rift valley fever, and chikungunya viruses, are most troubling right now.  Ae. aegyptii most of all, of course, but increasingly Ae. albopictus.

An extensive outbreak of rift valley fever in South Africa produced dozens of human cases earlier this year, and seems to be continuing among livestock.  An epidemiologist friend in Europe told me a few weeks back that he and other European disease control specialists, already concerned about dengue and yellow fever, are looking at RVF exposures in the southern part of the continent — a worrisome finding for a virus that has primarily been African.   The European Center for Disease Control is, appropriately, concerned about the establishment of Ae. albopictus in Europe.

Ditto chikungunya, which as produced 33 cases in Delhi, India, this year, possibly including an illness in the city’s mayor.

Dengue  demands control most pressingly of all.  Although the CDC is busily advising Americans not to worry (“Nearly all dengue cases reported in the 48 continental states were acquired elsewhere by travelers or immigrants,” its info page reads), there is active spread through much of the Caribbean basin — see the map at Dengue Watch, for instance.  The Mexican ministry of health reports dengue transmission in areas bordering the U.S.  There has already been an outbreak in Texas (in 2005).  And other highly industrialized countries with strong surveillance and control systems are experiencing dengue cases, including the first report of domestic transmission within France this summer.

(Hats off to Crof at H5N1, who has been following both chikungunya and dengue assiduously.)

The expansion of the range of Ae. albopictus, a secondary but by no means ignorable vector for dengue, makes the geographic extension of these pathogens worthy of concern.

With climate changing, trade routes always in flux, area spraying of insecticide disfavored because of environmental considerations, and of course mosquitoes evolving to take advantage of new niches, it seems unlikely that North Americans can go on counting on the mere improbability that virus and vector will coincide.

Mosquito control programs are in place, and U.S. authorities expend considerable effort at controlling Ae. aegyptii in Puerto Rico.  But the West Nile fever outbreak of 1999 and its subsequent extension in North America reveals the porousness of mosquito control.

Mosquitoes are much more worrisome than bed bugs.

A Blog Worth Following

If you haven’t already, put Crawford Kilian’s H5N1 blog on your regular reading list.  There, while you’ll still get updates on the H5N1 avian flu virus and occasional pieces on H1N1 flu (and you can see a multitude of archived posts from 2009  filled with international material on the progress of last year’s flu — and the reaction to it), you now get a much-expanded scope, including news and commentary on the spread of infectious diseases of different sorts.

What I value about H5N1 is the tracking of the mosquito-borne viral diseases, like dengue and chikungunya as well as H1N1, that reveal the effects of the elision of ecosystem boundaries; the close attention to outbreaks that stem from changes in human-animal interactions — like the recent outbreak of plague in Tibet and, of course, H5N1; and the watch it keeps on the vaccine trade, as in yesterday’s post picking up a report in The Nation on the purchase of flu vaccine from France and one last week on a US tech company’s trials of a new flu vaccine (which won’t help the public but is, apparently, already helping the company to get richer).

The kind of close attention to the details of complex interactions amongst humans, animals, and both the natural environment and the economic one that H5N1 shows is indispensable.   It should spur more interest in wresting public health away from the simple-minded mass-vaccination schemes of medical officials in the U.S. and other wealthy countries — the point of which is usually to transfer public monies into the hands of pharmaceutical companies.  And move us to toward a more complex and inclusive view of the nature of health.

Science Learning

My blog pal Joanne, the estimable Science Goddess, is running a very smart science reading contest (along with her colleague Jeff at Scienticity) for children and teens.

Actually, there are two contests, divided by age:

Click here for Joanne’s promotional video and here for a list of authors supporting the project.

Grown-ups make such a mess when they can’t, or won’t, understand straightforward chemistry and physics — worsening the Gulf of Mexico situation, for instance, by failing to learn how to do the cleanup while keeping workers safe, as ProPublica has been reporting lately and The Pump Handle follows assiduously.  So  it’s impossible to overstate the importance of kids’ learning to understand how to read science.

In regard to reading science, The American Scholar just published a thought-provoking essay by nobel-laureate physicist Robert B. Laughlin.  The article ponders geologic time from a scientist’s standpoint — and makes a crucial distinction between what we really cannot know about the earth’s future and what the rising costs (financial, environmental, human) of energy make us fear.

Laughlin writes

The geologic record as we know it thus suggests that climate is a profoundly grander thing than energy. Energy procurement is a matter of engineering and keeping the lights on under circumstances that are likely to get more difficult as time progresses. Climate change, by contrast, is a matter of geologic time, something that the earth routinely does on its own without asking anyone’s permission or explaining itself.

I suppose Laughlin will take a lot of flak from people who are sure that “the science” allows them to predict that the earth will be irrevocably ruined, and human civilization irretrievably altered (if not demolished), by manmade climate change. But it’s refreshing when a scientist can acknowledge that humans do bad things to the environment but still refuse to join the sky-is-falling brigade.

There are lots of reasons to curtail the damage that humans do to the physical environment and to preserve biodiversity.  But having a crystal-clear view of just what will happen if the carbon dioxide concentration stays above 350 ppm — islands disappearing and so forth — shouldn’t be one of them.

Science is good at explaining the world, but about the future it is best for telling us what we don’t know (and what questions to ask).

A little more awareness of what we don’t know, and a lot more humility in the face of ignorance, might have gone a long way toward protecting the Gulf of Mexico.  Too late for that.

So Brava! to Joanne, Bravo! to Jeff, for furthering the project of teaching the next generation to use science better.